Linux Hard Drive

Quick background on my situation:

1 laptop (Win8), 1 desktop (Win7)

Windows 7’s been good to me, but 8 is so painful on so many levels. After the hundredth problem in a couple months, I wanted to look into putting Ubuntu or some other Linux on here instead. I managed to get passed Secureboot (despite this being an Acer) and get Ubuntu running via usb. Could I just install and run it off of an external hard drive (I already have a USB 3.0 one)? I found a bunch of tutorials for running it off of a usb flash drive, but would a external HDD be better than that? I don’t think I would want to totally get rid of Windows yet.

I also tried running Zorin 7 and Fedora via both usb and livedvd, and neither would boot up. No Secureboot error, just skipped straight to Windows.

As for the desktop, Windows 7 has been stable for my purposes. Upon trying Zorin and Fedora, those worked. I may try Mint later as many people say it’s an easy starting point. I was wanting to look into buying a separate internal hard drive, as the one in there is full and I wouldn’t want to dual boot anyway. Would any hard drive work, and how should it be formatted? I’m looking at this page on Amazon:

I probably don’t need more than 1 TB. Any suggestions/help is appreciated!